Polymeric compositions

ABSTRACT

Described are compositions comprising core/shell particles and fluoropolymer, wherein the core comprises an ultraviolet absorber, as well as multiphase polymeric compositions comprising a polymeric core phase and a polymeric shelf phase, wherein the polymeric core phase comprises an ultraviolet absorber.

FIELD OF THE INVENTION

[0001] The invention contemplates UV-absorbing compositions includinglatices, agglomerate particles, powders, films, coatings, multilayerarticles, and other materials prepared from or containing the polymericparticles or derivatives thereof, and methods associated with theparticles and compositions.

BACKGROUND

[0002] Ultraviolet radiation (UV) can cause degradation of certainmaterials if exposed. Chemical materials known as ultraviolet absorbers,or UVAs, can be used to protect materials from the damaging effects ofUV radiation. A UVA can be incorporated into a material to protect thatmaterial from UV radiation, or, a composition that contains UVA can beapplied to a UV-sensitive substrate to protect the substrate.

[0003] Protective coating compositions, sometimes referred to as“topcoats,” can be applied to outdoor-durable materials such as signsbased on flexible substrates and optionally having applied graphics,where the coating functions to inhibit dirt buildup or dirt penetration,as a barrier to water, to prevent plasticizers or other ingredients frommigrating out of the substrate, or to allow ease of cleaning. A topcoatcan include polymeric materials (e.g., a fluoropolymer to provide dirtresistance or cleanability), as well as stabilizers to protect thetopcoat or the substrate from degradation, e.g., due to UV radiation.Degradation may involve yellowing, embrittlement, or loss of clarity,gloss, or water resistance.

[0004] Unfortunately, while it can be desirable to incorporate a UVAinto a protective coating, UVAs can cause some difficult problems. Oneproblem is the relative impermanence of UVAs in many chemicalcompositions. Non-reactive UVAs can be included in a chemicalcomposition as a dispersed compound, not chemically attached to anyother component. These UVAs can be lost from a composition byvolatilization during processing (e.g., drying), or by otherwisemigrating to the surface of a composition followed by removal as dust orwash off. Loss of the UVA leaves the composition and its substrate lessprotected from ultraviolet radiation, allowing UV radiation to degradethe composition or substrate. One imperfect remedy to this problem is toinclude larger amounts of UVA in a composition.

[0005] A further problem with UVAs is that they can be incompatible withdifferent polymeric materials (e.g., fluoropolymers). Thisincompatibility can lead to instability (e.g., thermodynamicinstability) or water sensitivity of the composition, which can cause aloss of physical or optical properties, including loss of clarity orincreased fogginess. Incompatibility can also cause increased oraccelerated loss of UVA by migration, bleeding, or blooming.

[0006] Attempts to incorporate UVAs into chemical compositions such astopcoats have been met with a variety of frustrating results, especiallywhen the composition includes an ingredient that is incompatible withthe UVA, as are many fluoropolymers. There is a general need to identifyultraviolet absorbing materials and compositions, and also to identifymaterials that can be used to prepare UV-absorbing compositions such asfilms and coatings. There is a further need to incorporate UVAs intochemical compositions that contain other materials with which the UVAmay not be compatible, wherein the UVA becomes a relatively permanentcomponent of the composition, and wherein the composition is relativelythermodynamically stable, to provide long-term protection fromultraviolet radiation.

SUMMARY OF THE INVENTION

[0007] The invention provides ultraviolet radiation-absorbingcompositions including latices of core/shell particles wherein the corecomprises a core polymer and a UVA, as well as multiphase polymericcompositions comprising a polymeric core phase and a polymeric shellphase, wherein the polymeric core phase includes ultraviolet absorber.

[0008] Preferred multiphase polymeric compositions comprising a corephase, a shell phase, and a phase of an additional polymeric materialcan exhibit improved thermodynamic stability and UVA retention, therebyexhibiting time-stable protection from ultraviolet radiation, withlasting physical and mechanical properties. This can be true even if theUVA is used in combination with an additional material that is notcompatible with the UVA.

[0009] An exemplary composition is a latex comprising core/shellparticles and a polymeric film-forming material, wherein the latex maybe coated and dried to form a film, or which may be spray dried to forma powder which can be further processed. Such a latex can be formed intoa film or coating e.g., by coating and drying, or, dried to form apowder, preferably spray-dried to form a powder comprising agglomerateparticles which can be coated onto a substrate and fused to form a filmor coating.

[0010] Multiphase polymeric compositions of the invention can comprisephase domains of a polymeric core phase, a polymeric shell phase, and apolymeric film-forming phase, wherein the morphology is such that thepolymeric core phase does not substantially contact the polymericfilm-forming phase, but both of these phases contact the polymeric shellphase, which separates the other two phases. It has been found thatcompositions having this preferred morphology, particularly if the coreparticle (or a component thereof) is not compatible with the polymericfilm-forming material, can exhibit improved initial physical properties,which can be maintained with aging, as compared to chemical compositionscontaining chemically identical ingredients, in identical amounts, butexhibiting a different morphology. Such properties can include one ormore of: flexibility, lasting protection from ultraviolet radiation dueto reduced migration loss (e.g., bleeding or blooming) of the UVA(especially if the UVA is not chemically attached to the core polymer);thermodynamic stability; and improved resistance to water (e.g., reducedwater sensitivity).

[0011] A particular advantage of this preferred morphology is that itallows the use of a core particle or a component thereof, e.g., a corepolymer or a UVA, to be used in a composition that contains anothermaterial (e.g., a polymeric film-forming material) that is incompatiblewith the core particle or core particle component. If a core particle orits component is incompatible with a polymeric film-forming material,the shell material shields the core particle phase from the incompatiblephase, thus preventing the consequences otherwise associated withincluding the core particle with an incompatible material, and therebypreferably achieving a thermodynamically stable composition.

[0012] Multiphase polymeric compositions having the described morphologycan be prepared by various methods. For instance, such a multiphasecomposition can be prepared from a latex that includes polymericparticles having a core/shell structure, wherein the core comprises UVA,and particles of polymeric film-forming material. This can beaccomplished by forming the latex into a film or coating, and allowingthe latex to dry. Alternatively, such a multiphase composition can beprepared by spray-drying the latex to prepare a powder of agglomerateparticles, powder coating the agglomerate particles, and fusing thecoated powder.

[0013] An aspect of the invention relates to compositions comprisingfluoropolymer and polymeric core/shell particles wherein the corecomprises a UVA. The composition can be in the form of one or more ofthe following: a latex; an agglomerate particle of the core/shellparticles fused to fluoropolymer particles; a powder comprisingcore/shell particles and fluoropolymer particles, or their agglomerates;a polymeric composition such as a multiphase polymeric composition,e.g., in the form of a film, coating, or multilayer article; or aproduct or composition derived from or containing any of thesecompositions. Such compositions can block or absorb ultravioletradiation for any desired reason and can exhibit desirable cleanabilityproperties, and desired mechanical or physical properties such asflexibility. The core/shell particles can be included in a compositionto protect that composition itself from UV radiation, or, aUVA-containing film or coating can be disposed onto another material toprotect that material from UV radiation.

[0014] Another aspect of the invention relates to a multiphase polymericcomposition comprising a polymeric core phase, a polymeric shell phase,and a fluoropolymer phase, wherein the polymeric core phase comprises anultraviolet absorber and wherein the polymeric core phase and thefluoropolymer phase do not substantially contact one another, but boththe polymeric core phase and the fluoropolymer phase contact thepolymeric shell phase.

[0015] Another aspect of the invention relates to a method for preparinga multiphase polymeric composition comprising a polymeric core phase, apolymeric shell phase, and a polymeric film-forming phase, wherein thepolymeric core phase comprises an ultraviolet absorber. The methodincludes steps comprising: powder coating onto a substrate polymericmaterials comprising the polymeric core phase, the polymeric shellphase, and the polymeric film-forming phase, and fusing the polymericmaterials to form a multiphase polymeric composition wherein thepolymeric core phase and the polymeric film-forming phase do notsubstantially contact one another, but both the polymeric core phase andthe polymeric film-forming phase contact the polymeric shell phase.

[0016] As used herein, the following terms shall be given the recitedmeanings:

[0017] The term “thermoplastic” means materials that soften or flow uponexposure to heat and/or pressure. Thermoplastic is contrasted with“thermoset,” which describes materials that react irreversibly uponheating so that subsequent applications of heat and pressure do notcause them to soften or flow.

[0018] “(Meth)acrylate” means either acrylate or methacrylate.

[0019] “Phase” is used in a manner not inconsistent with its generallyaccepted meaning in the chemical art, for instance to refer to adiscrete, typically homogeneous component of a chemical composition.

[0020] “Domain,” when referring to a phase of a multiphase composition,refers to individual, continuous or discontinuous, microscopic ormacroscopic portions of a phase within the multiphase composition.Examples of discontinuous domains include the following, as illustratedin FIG. 3: individual core particle domains; polymeric shell domains;and fluorochemical domains.

[0021] In a multiphase polymeric composition, if individual domains ofone phase have an affinity for each other (there is an affinity betweenseparate, individual domains of the same phase) that is significantlygreater than the affinity between domains of that phase and domains of achemically different phase of the composition which the first phasecontacts, individual domains of the like phases will bethermodynamically driven to combine with each other, causing polymersegregation and growth in domain size of like phase domains. Phases of amultiphase polymeric composition are referred to as “incompatible” if,while both are contained in a multiphase composition, they tend tocombine with each other within the composition to form larger phasedomains. If domains of a like phase of a multiphase polymericcomposition do in fact form larger-sized phase domains, i.e., thecomposition suffers gross symptoms of polymer segregation, themultiphase polymeric composition is considered to be “thermodynamicallyunstable.”

[0022] Gross symptoms of polymer segregation can include decreasedoptical clarity, loss of flexibility, embrittlement, and other effects.Polymer segregation within a multiphase polymeric composition can beconsidered to occur upon a significant loss of clarity or flexibility,or a significant increase in brittleness. These properties can bemeasured by known methods.

[0023] Brittleness can be measured by measuring elongation, with a 20%decrease in elongation being considered significant and indicatingpolymer segregation and thermodynamic instability.

[0024] Clarity can be measured using a Hazemeter. If the result of ahaze measurement according to ASTM D1003, upon aging, increases by 10percentage points, e.g., 5 percentage points or more (e.g., from areading of 0% to 5%, see the Examples Section and Table 1), it isconsidered to have lost a significant amount of clarity, and isconsidered to be thermodynamically unstable.

[0025] Flexibility of a multiphase polymeric film composition applied toa flexible substrate can be detected by the following test: samples ofthe film (approximately 20 to 50 micrometers in thickness) coated onto asubstrate (approximately 500 to 600 micrometers in thickness, e.g., 3MPANAFLEX™ 930 Sign and Awning Substrate) (optionally aged, e.g., for 1week at 150 F). Two samples of the coated film can be cooled to roomtemperature (about 25° C.), and then bent and creased, one in adirection to cause compression of the coating, and another to causeextension. Creasing can be a fold to 180 degrees, followed by heavyfinger pressure along the fold. If the coating visibly cracks, thecoating is considered to have lost flexibility. To more easily seecracks, a permanent marker can be applied to the creased coating, andthe marker can be washed off with isopropyl alcohol. If a crack ispresent, the marker will stain the crack and remain visible afterwashing; if no cracks are present, the marker will wash clean.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is an SEM photomicrograph at 2.0 kv×500 magnification ofagglomerate particles prepared by spray drying a latex containingcore/shell particles and fluoropolymer particles,

[0027]FIG. 2 is an SEM photo at 3.0 kv ×25.0 K magnification containingthe surface of agglomerate particles prepared by spray drying a latex ofcore/shell particles and fluoropolymer particles.

[0028]FIG. 3 is a transmission electron micrograph (TEM) taken at 60,000times magnification of a multiphase film prepared according to example.The smaller dark, circular regions are domains of the polymeric corephase of the core/polymeric shell (dyed with RuO₄); the core phasedomains are surrounded by lighter domains of polymeric shell. The largerdomains, generally relatively light, and generally not containingdomains of the darker core polymer phase are domains of a fluoropolymerphase.

[0029]FIG. 4 is a transmission electron micrograph (TEM) taken at 60,000times magnification of a multiphase film prepared according toComparative Example 2. The small phase domains are of the core particlephase; the larger, nondistinct, essentially continuous phase comprises amixture of polymeric shell and fluoropolymer.

[0030]FIG. 5 is a schematic view of a method of applying a multiphasepolymeric coating onto a substrate according to this invention.

[0031]FIG. 6 is a schematic cross-sectional view illustrating apreferred embodiment of the invention.

DETAILED DESCRIPTION

[0032] Polymeric core/shell particles used in the practice of theinvention exhibit a core/shell structure, meaning the particles comprisea polymeric core and a polymeric shell. The polymeric core comprisescore polymer and ultraviolet absorber (UVA), which may or may not bechemically incorporated into the core polymer. (The polymeric core caninclude non-polymeric materials, and may be referred to herein as the“core” or “core particle.”) These particles as described in Assignee'scopending United States Patent Application entitled UV-AbsorbingParticles, having Ser. No. ______, Attorney's Docket No. 54644USA6A,which was filed on even date herewith, and which is fully incorporatedherein by reference.

[0033] The core polymer can be chosen to be useful for a specificapplication of the core/shell particle to provide various physical,chemical, or mechanical properties. The core polymer can be chosen to bea relatively soft or rubbery material, e.g., having a glass transitiontemperature (Tg) of 40 degrees Celsius (40 C) or lower. A soft orrubbery core polymer may impart flexibility to a core/shell particle ora composition containing or derived from the core/shell particle.Alternatively, the core polymer may be relatively hard, or eventhermosetting or thermoset. A relatively hard core polymer can impartdirt resistance or cleanability properties to a core particle so that ifa portion of a core particle is exposed at the surface of a composition,it will not cause dirt buildup, or will at least be cleanable. The corepolymer can be crosslinked to prevent breakage or disruption of the coreparticle during processing, e.g., to a film or coating, which couldcause core material to be present at the surface of the film or coating.

[0034] The core polymer can comprise monomeric units derived from one ormore reactive monomers or comonomers (referred to collectively herein asthe “core monomer” or “core monomers”). The core monomer can include anyreactive compound (e.g., monomer, dimer, trimer, oligomer, prepolymer,polymer, etc.) capable of forming a useful core polymer (meaning ahomopolymer or a copolymer). Examples of useful core monomers includemonofunctional reactive compounds' comprising unsaturated moieties suchas vinyls, e.g., (meth)acrylates, with lower (meth)acrylates beingpreferred, or other reactive compounds such as epoxies, alcohols, orisocyanates. Specific examples include butyl acrylate, hexyl acrylate,octyl acrylate, decyl acrylate, and butyl methacrylate, with ethylacrylate and methyl methacrylate being preferred.

[0035] The core monomer can include multi-functional reactive compoundshaving suitable reactive moities, e.g., two, three, or more reactivemoieties such as vinyls, (meth)acrylates, epoxies, alcohols,isocyanates, etc. Such multi-functional compounds (sometimes referred toor used as crosslinkers) are known in the art of polymer chemistry, anduseful examples include but are not limited to multi-functional vinylcompounds such as multifunctional (meth)acrylate compounds,multifunctional styrenes, and multifunctional allyl compounds,specifically including allyl acrylate, allyl methacrylate (AMA),butanediol diacrylate (BDDA), and hexanediol diacrylate (HDDA).

[0036] Ultraviolet radiation absorbers, UVAs, are known and commerciallyavailable chemical materials which absorb ultraviolet radiation. See,e.g. Rabek, J. F., Photostabilization of Polymers, 20342 (1990),incorporated herein by reference. A variety of UVAs are known andcommercially available, and can be prepared by known methods. See id. AUVA can preferably be soluble in a core polymer, and can be chosen tohave desired UV-absorption properties for a given application of thecore/shell particles. Examples of UVAs include benzophenones,benzotriazoles, triazines, cinnamates, cyanoacrylates, dicyanoethylenes, and para-aminobenzoates. For protecting a PVC substrate,preferred UVAs include benzotriazoles and benzophenones.

[0037] The UVA can be included in, contained by, or attached to the coreparticle in any configuration, and in any chemical or physical manner. AUVA can be a relatively low molecular weight compound dispersed in, notchemically attached to, the core polymer. Such dispersible UVAs arecommercially available, with a single example being TINUVIN 1130, fromCiba Specialties Corp.

[0038] Optionally, a UVA can be functionalized with one or more reactivemoieties to provide a reactive, monomeric UVA which can be included inand reacted with the core monomer to become chemically incorporated intothe core polymer as a monomeric unit of the backbone or as a grouppendant from the core polymer. Suitable reactive moieties includeunsaturated moieties such as vinyls, e.g., (meth)acrylate and styrene,or other useful reactive moieties such as alcohols, isocyanates,epoxies, etc. Specific examples of functionalized UVAs include(meth)acrylate-functionalized UVAs such as (meth)acrylate-functionalbenzotriazoles and benzophenones. These compounds are well known, can beprepared by known methods, and are commercially available, e.g., NORBLOCUVAs such as NORBLOC 7966.

[0039] A core particle can be prepared from any useful amounts ofvarious core monomers, reactive (monomeric) UVA, non-reactive(dispersible) UVA, and crosslinker. Useful amounts of these differentingredients can be from about 50 to 98 parts by weight core monomerbased on the total weight of the core particle, preferably from about 65to 95 parts by weight, and more preferably from about 75 to 90 parts byweight core monomer (for purposes of these ranges the monomer does notinclude reactive (monomeric) UVA), and up to about 5 weight percentcrosslinker, preferably from about 0.1 to 3 weight percent crosslinker,e.g., from about 0.2 to about 2 weight percent crosslinker, based on thetotal weight of the core particle. The amount of UVA included in a coreparticle can be any useful amount, depending on factors such as thechemistry of the UVA, the substrate, the core monomer, etc. In general,UVA can be included in a core particle in an amount in the range fromabout 2 to 50 parts by weight UVA based on the total weight of the coreparticle, preferably from about 5 to 35 parts by weight UVA, and morepreferably from about 10 to 25 parts by weight; these ranges are thesame whether the UVA is monomeric, i.e., reactive with the core monomer,or non-reactive. A preferred core polymer may also be prepared from asingle acrylate or (meth)acrylate monomer, and optionally a reactive UVAand crosslinker, e.g., ethyl acrylate and a (meth)acrylate-functionalUVA, and crosslinker.

[0040] The polymeric shell takes the form of a polymeric materialdisposed on the core, preferably completely surrounding (e.g.,encapsulating) the core. Still, it is possible for production processesto result in particles wherein the polymeric shell does not completelysurround the core, but only partially covers the core, leaving a portionof the core exposed. These particles, if produced, will typically bepresent in relatively small amounts compared to core/shell particleswhere the polymeric shell does completely surround or encapsulate thecore.

[0041] The polymeric shell comprises a polymeric material (shellpolymer) useful for a chosen core/shell particle and application, toprovide desired physical, mechanical, or chemical properties. The shellpolymer may be chosen to be a thermoplastic polymer such as one having aTg sufficiently high to yield a powder composition that flows freely,without particles substantially gumming or clinging together, but stilllow enough that the core/shell particles and compositions or productscontaining or derived from the core/shell particles can be suitable forprocessing and still exhibit useful chemical, physical, and mechanicalproperties. The shell polymer can also be sufficiently hard (e.g., havea sufficiently high Tg) to exhibit dirt resistance and cleanabilityproperties. It may be desirable to crosslink the shell polymer in orderto provide desired physical properties. For instance the shell polymercould be crosslinked to increase solvent resistance, so the core/shellparticles may be added to solvent-based systems while still maintainingtheir core/shell structure.

[0042] The polymeric shell, or components thereof, may be eithercompatible or incompatible with the core particle, while preferablyexhibiting a useful level of adherence to the core particle. Theingredients of the polymeric shell may be chosen based on compatibilityor incompatibility with a polymeric film-forming material with which thecore/shell particles may be intended for use (e.g., mixed with, coatedon, or otherwise associated with). If the core/shell particles aredesigned for use in a composition comprising a polymeric film-formingmaterial, e.g., a fluoropolymer, the polymeric shell can preferably be,but is not required to be, compatible with that polymeric film-formingmaterial.

[0043] Monomers used to prepare the shell polymer (shell monomers) canbe chosen to provide a polymeric shell according to the aboveconsiderations, e.g., to provide desired physical properties such ashardness or softness, or compatibility or cleanability properties, andcan be chosen to be thermoplastic, thermosetting or crosslinked.Preferred shell monomers can include (meth)acrylate monomers such asmethyl methacrylate (MMA), methyl acrylate, ethyl methacrylate, ethylacrylate (EA), and mixtures of these. Particularly preferred shellmonomers include MMA and EA.

[0044] Selected shell monomers can be included in a variety of usefulamounts, with preferred amounts of methyl methylacrylate and ethylacrylate being in the range from 70:30 to 95:5 (MMA:EA) (by weight),more preferably in the range from about 80:20 to 90:10, MMA:EA.

[0045] The amounts (by weight) of core particle and polymeric shell in acore/shell particle can be any amounts of each which are found to beuseful for a particular application, and to provide desired physical ormechanical properties such as flexibility or cleanability, with anexemplary range being from about 1:1 to 1:9 parts by weight coreparticle per parts by weight polymeric shell (core:shell). Preferredamounts of core particle to polymeric shell can be in the range fromabout 30:70 to 15:85.

[0046] Polymeric core/shell particles can be prepared from theabove-described materials, by methods known in the polymer art. Thechosen method can depend on a number of factors including the identityof the core and shell monomers, whether the UVA is non-reactive andtherefore will be dispersed in the core polymer or reactive and will bean attached chemical component of the core polymer, or whether the corepolymer or polymeric shell is thermoplastic, thermosetting, orcrosslinked. Examples of suitable methods include those described, e.g.,in U.S. Pat. No. 5,461,125 (Lu et al.), and Segall et al., Core-ShellStructured Latex Particles. II Synthesis and Characterization ofPoly(n-butyl acrylate)/Poly(benzyl methacrylate-styrene) StructuredLatex Particles, J. Applied Poly Sci. 58, 401-417 (1995), incorporatedherein by reference. Specifically, the core/shell particles can beprepared by semi-continuous or two-stage emulsion polymerizationmethods, wherein a first polymerization produces a core particlecomprising the UVA, and by a second polymerization a polymeric shell isformed on the core.

[0047] Preferred methods for preparing core/shell particles can producean aqueous latex comprising a dispersion of core/shell particles inwater. The core/shell particles can be present in a range of differentlyshaped and sized particles, typically having an average (mean) size(diameter) in the range from about 40 to 200 nanometers. The size ofcore/shell particles can be measured by known analytical methods, forexample by light scattering methods using a light scattering apparatus,such as a COULTER N4 MD submicron particle analyzer.

[0048] The core/shell particles can be combined with a polymericfilm-forming material, and processed to film-forming, UV-absorbingchemical compositions.

[0049] Polymeric film-forming materials are well known, and aredescribed throughout the patent and scientific literature; See e.g.Organic Coatings: Science and Technology, Wicks, Jones, and Pappas 3548(1992), and Encyclopedia of Polymer Science and Engineering, SupplementVolume, pp. 53-59 (1989), both of which are incorporated herein byreference. Polymeric film-forming materials can typically be consideredto be polymeric material that can be formed into a continuous coating orfilm (e.g., a solid), e.g., by drying with removal of solvent, bychemical reaction, or by melting or fusing. The polymeric film-formingmaterial can be in any useful form, such as a solid (e.g., a powder), aliquid (e.g., a high solids liquid such as a polymeric resin or a lowsolids liquid such as an aqueous latex), or any combination of these orother forms. The polymeric film-forming material can be reactive ornon-reactive, thermoplastic, thermosetting, or otherwise polymerizable,and can be either compatible or incompatible with either the polymericshell or the core particle. The polymeric film-forming material can haveany useful chemistry, including chemistries similar to or identical to acomponent of the core or polymeric shells. Examples of some suitablepolymeric film-forming materials include but are not limited topolyvinyl chloride, polyamide, polyester, polyacrylate,polymethacrylate, polyethylene, polypropylene, fluoropolymers, andmixtures of one or more of these.

[0050] The core/shell particles can be particularly useful with afluoropolymer. Fluoropolymers and their preparation are well known.Examples of fluoropolymers include thermoplastic fluoropolymers such asthose available in the form of fluoropolymer powders and fluoropolymerlatices. Latices can for some applications be preferred over powders,because latices can be combined with a core/shell particle latex andthen processed further, e.g., spray dried to form agglomerate particlesas described infra.

[0051] Specific examples of useful thermoplastic fluoropolymers includehomopolymers and copolymers comprising monomeric units derived fromfluorinated monomers such as vinylidene fluoride (VF2),hexafluoropropene (HFP), chlorotrifluoroethylene (CTFE), vinyl fluoride(VF), trifluoroethylene (TrFE), and tetrafluoroethylene (TFE), amongothers, optionally in combination with one or more other non-fluorinatedmonomer. In general, any amounts of these and other fluorinated andnon-fluorinated comonomers can be used to prepare a fluoropolymer.Particularly preferred fluoropolymers can include fluoropolymer preparedfrom vinyl idene fluoride and BFP, with the amounts of VF2 and HFP beingapproximately 80 to 100 weight percent VF2 and 0 to 20 weight percentHFP, with preferred fluoropolymers being prepared from 95 to 100 wt %VF2 and 0 to 5 wt % HFP. Such fluoropolymers are available in the formof latices, typically having mean particle sizes in the range from 200to 400 nanometers.

[0052] Commercially available fluoropolymer powders and latices includeTHV-500P fluoroterpolymer powder and KEL-F 3700 from Dyneon, of St.Paul, Minn., KYNAR PVDF homo- and copolymer powders, and KYNAR 32 PVDFlatex from Elf Atochem.

[0053] The polymeric film-forming material may be combined with thecore/shell particles while either material is in any physical form orduring any stage of processing, for example when the core/shellparticles exist within a latex, or as a powder of core/shell particlesor their agglomerates, etc. Alternatively, the core/shell particles maybe added to a liquid or solid polymeric film-forming material, followedby extrusion.

[0054] The relative amounts of core/shell particles and polymericfilm-forming material in a given composition can be any amounts of eachthat are found to be useful, with amounts for any particular applicationdepending on factors such as the desired application or productconstruction, e.g., the physical or mechanical properties desired of acomposition or material prepared from the core/shell particles, thechemistries of the core and the polymeric shell, the chemistry of thepolymeric film-forming material, the choice of processing methods used,etc.

[0055] An exemplary composition of the invention is an aqueous latexcontaining core/shell particles and particles of polymeric film-formingmaterial e.g., in the form of dispersed polymeric particles. In apreferred embodiment, a latex containing core/shell particles can becombined with a fluoropolymer latex. It can be preferable for thelatices to be miscible with one another, and to be suitably stable inthe form of a combined latex. “Miscible” with respect to latices meansthat in combining the latices, a dispersion is maintained and thecombination of the two separate latices does not cause coagulation.(Coagulation of the latices can sometimes be prevented by pH adjustmentprior to mixing or by adding one latex to another very slowly.)

[0056] Aqueous latices can have solids contents as known in the polymerand latex arts, and can be prepared, combined, and processed intomixtures or other compositions by known methods. The latex may beprocessed as desired, for example dried by known methods to form apowder, or applied as a water-based coating to form a film upon drying.If applied as a coating and dried, the latex coating can be dried toremove water at one temperature, e.g., 66° C., followed by anotherheating step where the polymeric components are melted or fused togetherto form a continuous film or coating.

[0057] It will be appreciated by a skilled artisan that a latexcomposition comprising core/shell particles and polymeric film-formingmaterial can include other ingredients or additives useful in theproduction or processing of latices and films. The chosen ingredients oradditives can depend on the desired use of the latex, but can includefoam control agents, coalescing aids, anti-fungal agents, rheologycontrol materials such as thickeners, pigments, leveling agents, etc.

[0058] Preferred methods for drying a latex which contains core/shellparticles (alone or with another material) include spray drying methods.During spray-drying, latex particles tend to fuse together to formlarger agglomerate particles composed of the individual latex particles.A latex of core/shell particles and particles of a polymericfilm-forming material, if spray-dried, will typically produceagglomerate particles composed of particles of the polymericfilm-forming material fused with core/shell particles.

[0059] Agglomerate particles can preferably exist as a free-flowingpowder having a combination of particle size, thermoplastic properties(e.g., melt viscosity), and thermal stability, which allow the particlesto be processed into a desired product construction. Spray-drying canproduce agglomerate particles having a range of sizes, and the size ofthe agglomerate particles can be any size capable of being processedinto a useful product. After spray drying, agglomerate particles can begraded to obtain a desired, e.g., narrow, size distribution. An exampleof a useful size range for agglomerate particles can be in the rangefrom about 10 to 200 micrometers (μm), more preferably from about 10 to70 μm. Although particles outside of these size ranges may also beuseful, particles smaller than 10 μm may present explosion hazardsduring powder coating, and particles larger than 200 μm may be difficultto electrostatically charge for powder coating, and, if powder coated,may produce an overly thick particle layer that may be difficult tofuse.

[0060] Preferred agglomerate particles are shown in FIGS. 1 and 2. FIG.1 shows a number of agglomerate particles. The photomicrograph of FIG. 2is a closeup of a single agglomerate particle from FIG. 1. Thesephotomicrographs show agglomerate particles comprised of core/shellparticles and fluoropolymer particles fused together. In FIG. 2, thefluoropolymer particles are the larger spherical particles, and thesmaller spherical particles attached to and surrounding the largerfluoropolymer particles are the core/shell particles.

[0061] A skilled artisan will appreciate that a powder compositioncomprising the core/shell particles can additionally include, inunderstood amounts, other ingredients known to facilitate the productionor processing of a powder composition, such as plasticizers,stabilizers, flow aids to improve handling and processability (e.g.,silica), pigments, and extenders.

[0062] Another exemplary composition of the invention is a multiphasepolymeric composition which contains a polymeric core phase, a polymericshell phase, and a polymeric film-forming phase, e.g., in the form of afilm or a coating, and wherein the core phase comprises a UVA.Preferably, the composition exhibits a multiphase morphology whereincore phase domains and polymeric film-forming material phase domains donot substantially contact one another, but are substantially or entirelyseparated from each other by polymeric shell phase domains, e.g., bothpolymeric film-forming material phase domains and core phase domainscontact polymeric shell phase domains, but do not significantly contacteach other. Of course in practice there may be some degree of contactbetween domains of the core particle phase and the polymericfilm-forming material phase, e.g., due to imperfect processing of thecore/shell particles or due to breakage during processing, but this typeof inadvertent contact will typically be kept to insubstantial levels.

[0063] The core/shell particles used in this preferred morphology can beparticularly useful for allowing incorporation of a core particlematerial into a polymeric film-forming material with which the coreparticle material (e.g., a core particle, core polymer, or a UVAcontained in a core particle) is not compatible. The describedmorphology provides a polymeric composition that is relativelythermodynamically stable, because incompatible phases, e.g., the corephase and the polymeric film-forming material phase, are separated bythe polymeric shell phase; the incompatible phases do not contact eachother, thus resulting in thermodynamic stability and reducing thetendency of the multiphase composition to change morphology over time.

[0064] In these compositions, the core phase, the polymeric shell phase,and the polymeric film-forming material phase can be any of thosematerials described above, and can be chosen to provide particularproperties for a desired application. Preferred multiphase compositionscan include ingredients having appropriate chemistries for a particularapplication, and in appropriate amounts, to provide desired propertiessuch as flexibility, weather resistance, thermodynamic stability, andadhesion to a substrate. In a preferred multiphase composition, theamounts of polymeric core phase, polymeric shell phase, and polymericfilm-forming material phase can be sufficient to exhibit one or more ofthe following: flexibility, ultraviolet radiation absorption, dirt andwater resistance, prevention of plasticizer blooming or bleeding from asubstrate, and minimization of blooming, bleeding, or other migration ofUVA from the composition. Because these properties can be dependent on anumber of factors, such as the particular chemistries of the differentcomponents, a broad range of amounts of the different ingredients may beuseful. An exemplary range can be from about 80:20 to 10:90 (by weight)combined polymeric core and polymeric shell phases, per polymericfilm-forming material phase. Preferred amounts can be in the range fromabout 20:80 to 60:40 (combined polymeric core and shell phase: polymericfilm-forming material phase).

[0065] As one example, a multiphase polymeric composition may be used asa topcoat to be applied to a flexible substrate exposed to outdoorconditions. Such a topcoat can include ingredients including polymericcore phase, polymeric shell phase, and polymeric film-forming polymericmaterial phase, chosen to provide properties such as weatherability,durability, dirt resistance, water resistance, flexibility, toughness,adhesion to a desired substrate, barrier properties (e.g., resistance toplasticizers), compatibility between different phases, thermodynamicstability, etc. A preferred polymeric core phase for use in a topcoatcan be of a rubbery crosslinked material which provides flexibility tothe final construction, without brittleness. A polymeric shell phase fora topcoat can be chosen, e.g., to provide chosen properties such ascleanability, and to enhance adhesion between the multiphase polymericcomposition and a chosen substrate such as PVC. The polymericfilm-forming material can be chosen to add other specifically desiredproperties, e.g., a fluoropolymer may be chosen to provideweatherability, dirt and water resistance, and cleanability. Thepolymeric shell phase can preferably be, but is not required to be,compatible with the film-forming polymeric material phase. Preferredpolymeric shell materials that are compatible with many fluoropolymerscan have a Tg below about 105 C, with Tgs in the range from about 40 Cto 90 C being particularly preferred.

[0066] A specific example of a preferred multiphase composition is afilm comprising separate phase domains of a poly (ethyl acrylate) corephase, a poly(meth)acrylate shell phase, and fluoropolymer. Both thefluoropolymer and the core polymeric phases can be compatible with thepolymeric shell phase, but the fluoropolymer phase may or may not becompatible with the polymeric core phase.

[0067] It has been found that such multiphase polymeric compositionscomprising a polymeric core phase separated from a polymericfilm-forming phase by a polymeric shell phase can exhibit lasting UVAprotection due to reduced migration loss (e.g., bleeding or blooming) ofthe UVA; thermodynamic stability; and improved resistance to water(e.g., reduced water sensitivity), compared to chemical compositionscontaining the same amounts of chemically identical ingredients butexhibiting a different morphology. The improved properties are believedto be due, at least in part, to the fact that the UVA in the polymericcore phase is surrounded and contained by polymeric shell phase (and isoptionally and preferably chemically bound to the core polymer).Further, separation of incompatible phases can improve thermodynamicstability, which leads to improved water resistance (e.g., less watersensitivity). See, e.g., Comparative Example 2, infra.

[0068] Multiphase polymeric compositions having the preferredmorphology, optionally including a polymeric core phase that isincompatible with a polymeric film-forming material phase, can beprepared by any successful method. As an example, the morphology can beachieved by providing a film or coating comprising core/shell particlesand particles of the polymeric film-forming material, and processing thefilm or coating such that polymeric components of the composition fusetogether or solidify into a preferably continuous, cohesive film orcoating. The process can be practiced with care to maintain thecore/shell structure, e.g., prevent dissolution of the core/shellparticles, to achieve the preferred multiphase morphology.

[0069] More specifically, by one example of such a method, a multiphasecomposition having the preferred morphology can be achieved by providinga film or coating of a latex comprising core/shell particles andparticles of the polymeric film-forming material, followed by drying toform a film.

[0070] The preferred morphology can also be achieved by powder coatingparticles comprising core/shell particles and particles of the polymericfilm-forming material, (e.g., agglomerate particles obtained byspray-drying), followed by fusing. Fusing should take place at atemperature that is above the melting point of any crystalline polymericphase of the powder, and above the Tg of any amorphous polymeric phase,to a temperature sufficient to melt and thereby fuse the particles intoa preferably continuous, multiphase polymeric film or coating, to anextent that the core phase does not come into substantial contact withthe film-forming polymeric material phase.

[0071]FIG. 5 schematically illustrates a method of coating a powder ontoa flexible substrate. Substrate 10 moves through powder cloud 12 comingfrom electrostatic fluidized bed powder coater 14, so that a particlelayer 16 is formed on a surface of the substrate. The particles ofpowder cloud 12 are shown much larger than actual size for the purposeof illustration. Substrate 10 may be in the form of a long continuousweb (as shown), or a smaller piece of material laid on a carrier web. Ina another technique (see for example “Powder Coating,” edited byNicholas P. Liberto, published by the Powder Coating Institute, Chapter10 (1994)), powder cloud 12 can be generated by placing a powder in thechamber of the coater and passing ionized air through the powder untilit fluidizes. Preferably, the powder is pre-dried in a conditioningchamber (not shown) before use. The substrate passing through powdercloud 12 can be electrostatically charged to cause the powder to beattracted to the substrate. To facilitate deposition of a uniformcoating, a charge can be applied to the substrate by known methods,e.g., by corona treatment methods or by contacting the web to a materialwhich appears higher or lower on the triboelectric series, depending onthe desired polarity of the charge. A grounding plate 17 made ofaluminum or another like material can be placed behind the substrate toprovide a ground potential to attract the charged powder to the surfaceof the substrate. The coating weight of particle layer 16 can becontrolled by one or more of the line speed, the voltage applied to theair supply, and the particle size of the powder. Optionally, bothsurfaces of a substrate may be coated by passing the substrate betweentwo powder coaters, or by making two passes over the same coater andinverting the substrate between passes.

[0072] Although electrostatic fluidized bed powder coating is apreferred method for continuous powder coating, other types of powdercoating methods such as electrostatic spray coating may also be used.Powder coating equipment is well known and complete systems are readilyavailable commercially. A nonlimiting example of a powder coatingequipment manufacturer is Electrostatic Technology Incorporated (ETI),Branford Conn., USA.

[0073] Again referring to FIG. 5, to fuse the coated powder into acontinuous film or coating, the coated substrate passes through a nipconfiguration defined by heated roll 20 and backup roll 18. The nipconfiguration applies heat and pressure simultaneously to fuse thepowder particles of particle layer 16 into a continuous, multiphasepolymeric layer 22, and bond the layer to substrate 10, thereby forminga composite sheet material 30. No preheating stage is required prior tothe nip, but such a stage may be useful if desired, e.g., to achieve ahigher line speed. Heated roll 20 is typically made of metal, and itsouter surface is preferably covered with a material having releaseproperties such as poly(tetrafluoroethylene) to prevent transfer ofeither melted thermoplastic powder or fused thermoplastic layer from thesubstrate to the roll. Backup roll 18 preferably has a resilientsurface, such as rubber.

[0074] The temperature and pressure of the heated roll can be chosen tobe sufficient enough to fuse the coated powder into a continuous layer,yet not so high as to distort or degrade the substrate. If substrate 10is a thermoplastic film or other material likely to soften or distort atthe elevated temperatures in the nip, support can be provided to thesubstrate in the form of a carrier web, liner, or belt system (notshown). The backup roll may be at ambient temperature, it may be heatedto facilitate fusing, or it may be chilled to provide further thermalprotection for the substrate.

[0075] As an alternative to the nip configuration shown in FIG. 5,simultaneous heat and pressure may be applied by other suitable means,such as a heated press, or by a belt configuration.

[0076] While the above-detailed processes can be used to prepare amultilayer polymeric composition having the described preferredmorphology, this morphology may not be achieved by just any coating orfilm-forming process or method. For instance, the described preferredmorphology may not necessarily result from the same composition (i.e.,identical chemical ingredients in identical amounts) being prepared intoa film, if prepared by other processing methods. If, as described, alatex of the core/shell particles is blended with a latex of particlescomprising the polymeric film-forming material, followed by spray dryingto produce agglomerate particles, the resulting agglomerate particlescan be powder coated and fused to achieve a composition with the desiredmorphology. If, on the other hand, the latices are spray driedseparately, and then blended into a powder mixture and powder coated,the desired morphology may not necessarily be achieved, but a differentmorphology might be achieved which although possibly useful, may notexhibit the same physical properties of the described preferredmorphology. Furthermore, if the core/shell particles become dissolved orare otherwise caused to lose their core/shell structure duringprocessing, e.g., by mixture with a solvent, sufficient heating for anextended period of time, or by exposure to any other processingcondition that would cause the loss of the core/shell structure, acomposition prepared by such a method may not exhibit the describedpreferred morphology or resultant properties. In particular, if thecore/shell particles are solvent coated, it is possible that the desiredmorphology may not be achieved. See Comparative Example 3.

[0077] The core/shell particles can be used to prepare various productshaving UV radiation absorption or blocking properties. An example iscomposite sheet material 33, shown in FIG. 6. Multiphase polymeric layer22, (e.g., as a topcoat), in the form of a continuous film prepared fromor containing polymeric core/shell particles, is bonded to substrate 10.The multiphase polymeric layer can be transparent or translucent inappearance, and can generally have a thickness in the range from about12.7 μm to about 254 μm (0.5 mil to 10 mils). An example of a protectivecoating for an outdoor sign substrate (topcoat) can be translucent andcan have a thickness in the range from 10 μm to 25.4 μm (0.4 mil to 1mil).

[0078] Substrates that can be suitable include most any material thatcan benefit from protection from ultraviolet radiation, such asplastics, or materials that might otherwise be coated with a polymericmaterial, wherein the polymeric material can be UV-radiation resistant.Preferred substrates can be flexible two-dimensional materials capableof receiving a powder coating and capable of withstanding heat andpressure conditions used to process the powder into a coating or film.The substrate can be used in conjunction with a supporting liner, or canbe internally reinforced in order to meet process requirements. Thethickness of the substrate can be any useful thickness, and canpreferably be in the range from about 12.7 to about 1270 μm (0.5 to 50mil), more preferably from about 50.8 to about 762 μm (2 to 30 mil).

[0079] Preferred substrates include, flexible thermoplastic films suchas those made from polyester, polyamide, polyimide, polycarbonate,plasticized polymers such as PVC, polyacrylates such as polymethylmethacrylate, polypropylene, polyethylene, and copolymers orcombinations thereof. The thermoplastic film may optionally containadditional components such as pigments, fillers, reinforcing fibers ormesh, and ultraviolet absorbing agents, to provide properties importantfor some applications. An example of a suitable substrate for use inoutdoor backlit signs and awnings is a polyester mesh scrim that hasbeen coated on both sides with a plastisol containing PVC resin, aphthalate ester plasticizer, and pigment, and then fused. Such asubstrate is commercially available under the trade name PANAFLEX, from3M of St. Paul, Minn.

[0080] The powder may also be coated onto a release liner and optionallyfused into a film. The coat liner could then be used as a casting linerfor another film or coating such as a PVC plastisol or organosol.Optionally, the pre-fused film could be laminated to a previously fusedorganosol or plastisol film.

[0081] The substrate surface may optionally be treated to increaseadhesion between a topcoat and a substrate, e.g., by etching or othertreatment such as a non-polymeric, chemical agent applied to chemicallymodify the surface of the substrate to allow the topcoat to bond, or byapplication of an adhesion-promoting primer or tie-layer. Such treatmentis not required, and is preferably avoided if adhesion between thesubstrate and the topcoat is otherwise adequate. These and otherembodiments and applications of the compositions of the invention willbe apparent to a skilled artisan. See also Assignee's copending UnitedStates Patent Application, entitled Multi-layer Articles IncludingUV-Absorbing Polymeric Compositions, having U.S. Ser. No. ______,Attorney's Docket No. 54645USA4A, which was filed on even date herewithand which is fully incorporated herein by reference.

EXAMPLES Example 1

[0082] Preparation of a Polymeric UV Absorber (UVA) Having a Core/ShellStructure

[0083] This example details preparation of a latex particle having a30/70 core/shell ratio with the core composition being 17/83 Norbloc™7966/ ethyl acrylate and the shell composition being 80/20 methylmethacrylate/ethyl acrylate. Water (331.4 g), sodium lauryl sulfate (1.5g), isooctyl thioglycolate (0.45 g), and a mixture (premix) of ethylacrylate (37.5 g) and Norbloc™ 7966 (7.5 g) a polymerizable UV absorber(available from Janssen Pharmaceutica, Titusville, N.J.) were charged toa reaction flask, stirred and purged with nitrogen while heating to85-96° C. When the system was well dispersed, the batch was cooled to75° C. and a premix of potassium persulfate initiator (0.45 g) in water(17.55 g) was added. After an initial induction period, thepolymerization started and the batch temperature rose to about 80° C.After the peak temperature had been reached (about 5 to 10 minutes), theshell monomer premix consisting of methyl methacrylate (84 g), ethylacrylate (21 g) and isooctyl thioglycolate (0.53 g) was added over about90 minutes while the batch temperature was held at 80° C. When additionwas complete, the batch was held at 80° C. for 90 minutes then cooledand filtered through cheesecloth.

[0084] The product had inherent viscosity of 0.36 deciliter per gram(dl/g) measured in tetrahydrofuran solvent. Analysis of the driedpolymer by differential scanning calorimetry showed two separate glasstransitions at −6° C. and 70° C.

Example 2

[0085] Preparation of a Polymeric UV Absorber (UVA) having a Core/ShellStructure and a Crosslinked Core.

[0086] A latex with 20/80 core/shell ratio was prepared by the procedureof Example 1 above, modified as follows. The core composition wasprepared using 0.45 g allyl methacrylate, 5.01 g NORBLOC™ 7966, 24.54 gethyl acrylate, and 0.20 g isooctyl thioglycolate. The shell monomersincluded 102 g methyl methacrylate, 18 g ethyl acrylate and 0.78 gisooctyl thioglycolate. The shell monomer mixture was added over aperiod of 90 minutes. The product had IV =0.30 dl/g and a single glasstransition temperature at 82° C. The addition of allyl methacrylate tothe core resulted in crosslinking of the core and disappearance of thelower Tg that was noted in Example 1.

Examples 3 and 4

[0087] Preparation of Core/Shell Latices with Alternative PolymerizableUV Absorbers

[0088] Latices with a 30/70 core/shell ratio were prepared by theprocedure outlined in Example 1, modified as follows. The corecompositions for these examples were prepared from polymerizable UVA andethyl acrylate in a weight ratio of 16.7/83.3, and the shell polymer wasprepared from methyl methacrylate/ethyl acrylate in a weight ratio of80/20. The shell monomer mixture for both Example 3 and 4 contained 84 gmethyl methacrylate, 21 g ethyl acrylate and 0.53 g isooctylthioglycolate.

[0089] The core monomer mixture of Example 3 contained 37.5 g ethylacrylate, 7.5 g CGL 104, a polymerizable benzotriazole available fromCiba Specialty Chemicals, and 0.45 g isooctyl thioglycolate. The producthad IV =0.38 dl/g and showed two glass transition temperatures at −2° C.and 73° C.

[0090] In example 4, Cyasorb™ 416, a polymerizable benzophenone UVabsorber available from Cytec, was substituted for the CGL 104 used inExample 3. The product had IV=0.18 dl/g and showed two glass transitiontemperatures at 1° C. and 73° C.

Example 5

[0091] Non Polymerizable UVA in Core/Shell Particle Having a CrosslinkedCore.

[0092] A latex with a crosslinked core containing a non polymerizableUVA was prepared using the procedure of Example 2 except Tinuvin™ 1130,a non-polymerizable benzotriazole UV absorber available from CibaSpecialty Chemicals was substituted for NORBLOC™ 7966. The product hadIV=0.30 dl/g and a single Tg at 74° C.

Comparative Example 1

[0093] Preparation of a POLYMERIC UV ABSORBER Without a Core/ShellStructure

[0094] Homogeneous latex particles were prepared, having a compositionof 80/15/5 methyl methacrylate/ethyl acrylatel Norbloc™ 7966. Theseparticles were prepared using a two step (core/shell) process whereinthe composition of the core and the shell were identical. The procedureused was similar to that used in Example 1 except that the core monomermixture consisted of 36 g methyl methacrylate, 6.75 g ethyl acrylate,2.25 g NORBLOCTM 7966, and 0.45 g isooctyl thioglycolate, and the shellmonomer contained 84 g methyl methacrylate, 15.75 g ethyl acrylate, 5.25g Norbloc™ 7966 and 0.53 g isooctyl thioglycolate. The product had IV of0.31 dl/g and a single glass transition temperature at 87° C.

[0095] Preparation of Powder Coating Compositions

Example 6

[0096] A latex was prepared by blending the core/shell UVA latex ofExample 1 with a fluoropolymer latex consisting of Hylar™ FXH-6, a 95/5vinylidene fluoride/hexafluoropropylene copolymer from Ausimont USA, inratios of 80% fluoropolymer solids to 20% acrylic solids. The resultinglatex mixture was then spray dried to yield agglomerate powder particlesin which the two polymeric components were blended and fused onsubmicron scale. (See FIGS. 1 and 2). Spray drying was accomplishedunder the following conditions on a Büchi B-191 Mini Spray Dryer(available from Brinkman Instruments, Westbury, N.Y.):

[0097] Inlet Temperature: 140° C. Outlet Temperature: 40-55° C.

[0098] Pressurized air flow: 550 liters/hr. Pump Speed: 100%

[0099] Aspirator: 100% Vacuum 40-50 mbar

Comparative Example 2

[0100] A similar powder coating composition was prepared using thehomogeneous latex particles prepared in Comparative Example 1 and thefluoropolymer described in Example 6.

[0101] Preparation of Powder Coated Articles

[0102] The powder coating compositions prepared as described in Example6 and Comparative Example 2 above were coated onto 10.1 cm×15.2 cmpieces of PANAFLEX™ 930 vinyl outdoor sign substrate available from 3MCompany, St. Paul, Minn. A coating weight of 33 grams per square meterof the 80/20 fluoropolymer/acrylic powder blend was applied to thesubstrate using a laboratory-scale C-30 electrostatic fluidized bedpowder coater (Electrostatic Technology, Inc., Bradford, Conn.). Thevoltage in the coater was set to give the desired coating weight(settings varied with the powder used), and the substrate was held overthe coater for approximately 5 seconds. The coated substrate was thenhand fed through a nip configuration to fuse the particle layer. The nipconfiguration consisted of a TEFLON-coated roll heated to 200° C. and anunheated backup roll. A piece of aluminum foil was threaded over theheated roll. The coated substrate was placed powder side down on thefoil and fed through the nip at an applied air pressure of about 276 kPa(40 psi) and a line speed of 1 meter per minute. The resulting fusedprotective layer had a thickness of approximately 25 μm.

[0103] The same compositions were coated onto a TELFON-coated releaseliner and removed as a free film, which had the following UV-absorbingproperties.

[0104] The ultraviolet spectra of the films were essentially identicalto those of monomeric or polymeric benzotriazole UV absorbers and showedabsorption maxima at 240, 298 and 336 nm due to the benzotriazolechromophore.

Example 7

[0105] Preparation of Cast Films Using a Core/Shell Latex

[0106] Latices were prepared by blending the core/shell UVA latex ofExample 1 with a fluoropolymer emulsion of HYLARTM FXH-6, a 95/5vinylidene fluoride/hexafluoropropylene copolymer from Ausimont USA, inratios of 80% fluoropolymer solids to 20% acrylic solids. This latexblend was bar-coated onto a hydrophylically-primed polyester liner at awet thickness of 100 microns. The coating was then dried in a 67° C.oven for 3 minutes before transfer to a 180° C. oven for 1 minute. Theresultant continuous, dry film was 10-15 microns thick.

Comparative Example 3

[0107] Preparation of Solvent Cast Films

[0108] The powder coating composition prepared according to Example 6was dissolved in acetone (44° C.) in an amount sufficient to prepare a10% solids solution. The resultant solution was bar-coated onto apolyester liner at a wet thickness of ˜100 microns. The coating was thenheated for 1 minute at 190° C. to yield a dry film having a thickness ofapproximately 10-15 microns.

Example 8

[0109] Resistance of Coated Films to Hot Water

[0110] The water resistance of fused films was evaluated by immersion offused film samples into deionized water at 66° C. for 16 hours. Thistest simulates long term exposure to hot and humid conditions. The hazeor clarity of fused films was measured before and after immersion usinga Gardner PG 5500 Digital Photometric Unit and ASTM D1003 as a standardtest method.

[0111] Samples were prepared by powder coating the blended testmaterials prepared according to Example 6 and Comparative Example 2 ontoa TEFLON-coated flexible substrate and then fusing the coatings usingthe methods described previously (see Preparation of Powder CoatedArticles). The fused films (25 μm thick) were then removed from theTEFLON-coated substrate and evaluated for water resistance. The resultsfor the Example 6 composition containing core/shell UVA particles from(Example 1) and, the Comparative Example 2 composition, containing thehomogeneous UVA-containing particles (from Comparative Example 1) areshown in the Table 1 below. It is worth noting that the absolute haze isnot particularly relevant, because a film may be useful with variouslevels of haze or translucence; this test instead measures stability bytracking a change, e.g., increase, in haze. TABLE 1 Powder Coating HazeBefore Haze After Composition Immersion Immersion Difference Example 625.6% 28.1%  2.5% Comp. Ex. 2 22.0% 51.6% 29.6%

[0112] The results in Table 1 indicate that the film containing thecore/shell UVA (Ex. 6) exhibited much less change in haze caused by theimmersion challenge. This indicates that when powder coated and fused,the core/shell particle containing a UV absorber in the core, can beincluded in a fluoropolymer to produce a more thermodynamically stablemultiphase composition, than homogeneous UV absorbers.

[0113] Additionally, the core/shell particles showed improvedflexibility in qualitative comparison to the homogeneous particles incoated films made with the fluoropolymer/acrylic blends. Folding (usingfinger pressure) the coated substrate 180 degrees to form a sharp creasetested the coating flexibility. The substrates were creased with thecoating on the inside to test the coating versus compressive forces andwith the coating on the outside to test versus extensional forces. Thefilm containing the homogeneous acrylic cracked under both compressionand extension, the film containing the core/shell did not crack undereither stress.

[0114] The water resistance of the latex cast films (Example 7) and thesolvent cast films (Comparative Example 3) are shown in Table 2 below.TABLE 2 Haze Before Haze After Composition Immersion ImmersionDifference Example 7 1.1% 11.2% 10.1% Comp. Ex 3 1.5% 13.5% 12.0%

1. A chemical composition comprising: a polymeric particle having acore/shell structure, the core comprising an ultraviolet absorber; andfluoropolymer.
 2. The composition of claim 1 wherein the core isincompatible with the fluoropolymer.
 3. The composition of claim 1wherein the core comprises a polymer derived from monomers comprisingethyl acrylate.
 4. The composition of claim 3 wherein the core polymeris derived from monomers further comprising a (meth)acrylate-functionalultraviolet absorber.
 5. The composition of claim 3 wherein the corecomprises a polymer prepared from monomers consisting essentially ofethyl acrylate, (meth)acrylate-functional ultraviolet absorber, andcrosslinker.
 6. The composition of claim 2 wherein the shell comprises apolymeric shell that is compatible with the fluoropolymer.
 7. Thecomposition of claim 2 wherein the polymeric shell comprises apoly(meth)acrylate.
 8. The composition of claim 7 wherein the polymericshell is prepared from monomers chosen from the group consisting ofmethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, and mixtures thereof.
 9. The composition of claim 1wherein the fluoropolymer is prepared from fluorinated monomerscomprising vinylidene fluoride, hexafluoropropene, and mixtures thereof.10. The composition of claim 1 wherein the composition is an aqueouslatex.
 11. The composition of claim 1 wherein the composition is apowder.
 12. The composition of claim 11 wherein the compositioncomprises agglomerate particles comprising core/shell particles andfluoropolymer particles fused together.
 13. The composition of claim 1wherein the core/shell particles comprise from about 10 to 50 parts byweight core particle, and from about 50 to 90 parts by weight polymericshell.
 14. The composition of claim 13 wherein the composition comprisesfrom about 10 to 80 parts by weight core/shell particles and from about20 to 90 parts by weight fluoropolymer.
 15. A multiphase polymericcomposition comprising a polymeric core phase, a polymeric shell phase,and a fluoropolymer phase, wherein the polymeric core phase comprises anultraviolet absorber, and wherein the polymeric core phase and thefluoropolymer phase do not substantially contact one another, but boththe polymeric core phase and the fluoropolymer phase contact thepolymeric shell phase.
 16. The composition of claim 15 wherein domainsof the polymeric shell phase surround domains of the polymeric corephase.
 17. The composition of claim 15 wherein the polymeric core phaseis incompatible with the fluoropolymer phase, and wherein the polymericshell phase is compatible with both the polymeric core phase and thefluoropolymer phase.
 18. The composition of claim 17 wherein thecomposition is thermodynamically stable.
 19. The composition of claim 15wherein the polymeric core phase comprises a core polymer derived frommonomers comprising ethyl acrylate.
 20. The composition of claim 19wherein the core phase is a polymer prepared from monomers consistingessentially of ethyl acrylate and a (meth)acrylate-functionalultraviolet absorber.
 21. The composition of claim 15 wherein thecomposition is a flexible film.
 22. The composition of claim 15 whereinthe polymeric shell phase comprises a shell polymer prepared frommonomers chosen from the group consisting of methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, and mixtures thereof.23. The composition of claim 15 wherein the fluoropolymer is preparedfrom fluorinated monomers comprising vinylidene fluoride,hexafluoropropene, and mixtures thereof.
 24. A method of preparing amultiphase polymeric composition comprising a polymeric core phase, apolymeric shell phase, and a polymeric film-forming phase, wherein thepolymeric core phase comprises an ultraviolet absorber, the compositionbeing prepared according to steps comprising: powder coating onto asubstrate polymeric materials comprising the polymeric core phase, thepolymeric shell phase, and the polymeric film-forming phase, and fusingthe polymeric materials to form a multiphase polymeric compositionwherein the polymeric core phase and the polymeric film-forming phase donot substantially contact one another, but both the polymeric core phaseand the polymeric film-forming phase contact the polymeric shell phase.25. The method of claim 24 wherein the polymeric materials includecore/shell particles comprising a core particle surrounded by apolymeric shell.
 26. The method of claim 25 wherein the polymeric corephase comprises a core polymer prepared from monomers comprising ethylacrylate.
 27. The method of claim 25 wherein the polymeric materials arecoated as a powder comprising agglomerate particles of core/shellparticles and particles of the polymeric film-forming material.
 28. Themethod of claim 27 wherein the agglomerate particles are prepared byspray drying a latex comprising core/shell particles and particles ofpolymeric film-forming material.
 29. The method of claim 24 wherein thepolymeric film-forming material is a fluoropolymer.
 30. The method ofclaim 24 wherein the multiphase polymeric composition isthermodynamically stable.
 31. The method of claim 24 wherein themultiphase polymeric composition is flexible.